/*
 * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package com.nulldev.util.graphics.renderIt.ginterfaces.marlin.impl.pisces;

import static com.nulldev.util.graphics.renderIt.ginterfaces.marlin.impl.pisces.MarlinConst.LOG_UNSAFE_MALLOC;

import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Vector;

import com.nulldev.util.internal.unsafecompat.IUnsafe;
import com.nulldev.util.internal.unsafecompat.UnsafeCompat;

/**
 *
 */
final class OffHeapArray {

	// unsafe reference
	static final IUnsafe UNSAFE;
	// size of int / float
	static final int SIZE_INT;

	static {
		UNSAFE = UnsafeCompat.get();

		SIZE_INT = 4; // jdk 1.6 (Unsafe.ARRAY_INT_INDEX_SCALE)

		// Mimics Java2D Disposer:
		AccessController.doPrivileged(new PrivilegedAction<Void>() {

			@Override
			public Void run() {
				/*
				 * The thread must be a member of a thread group which will not get GCed before
				 * VM exit. Make its parent the top-level thread group.
				 */
				final Thread t = new Thread(MarlinUtils.getRootThreadGroup(), new OffHeapDisposer(), "MarlinRenderer Disposer");
				t.setContextClassLoader(null);
				t.setDaemon(true);
				t.setPriority(Thread.MAX_PRIORITY - 2);
				t.start();
				return null;
			}
		});
	}

	/* members */
	long address;
	long length;
	int used;

	OffHeapArray(final Object parent, final long len) {
		// note: may throw OOME:
		this.address = UNSAFE.allocateMemory(len);
		this.length = len;
		this.used = 0;
		if (LOG_UNSAFE_MALLOC) {
			MarlinUtils.logInfo(System.currentTimeMillis() + ": OffHeapArray.allocateMemory =   " + len + " to addr = " + this.address);
		}

		// Create the phantom reference to ensure freeing off-heap memory:
		REF_LIST.add(new OffHeapReference(parent, this));
	}

	/*
	 * As realloc may change the address, updating address is MANDATORY
	 * 
	 * @param len new array length
	 * 
	 * @throws OutOfMemoryError if the allocation is refused by the system
	 */
	void resize(final long len) {
		// note: may throw OOME:
		this.address = UNSAFE.reallocateMemory(address, len);
		this.length = len;
		if (LOG_UNSAFE_MALLOC) {
			MarlinUtils.logInfo(System.currentTimeMillis() + ": OffHeapArray.reallocateMemory = " + len + " to addr = " + this.address);
		}
	}

	void free() {
		UNSAFE.freeMemory(this.address);
		if (LOG_UNSAFE_MALLOC) {
			MarlinUtils.logInfo(System.currentTimeMillis() + ": OffHeapArray.freeMemory =       " + this.length + " at addr = " + this.address);
		}
		this.address = 0L;
	}

	void fill(final byte val) {
		UNSAFE.setMemory(this.address, this.length, val);
	}

	// Custom disposer (replaced by jdk9 Cleaner)

	// Parent reference queue
	private static final ReferenceQueue<Object> REF_QUEUE = new ReferenceQueue<Object>();
	// reference list
	private static final Vector<OffHeapReference> REF_LIST = new Vector<OffHeapReference>(32);

	static final class OffHeapReference extends PhantomReference<Object> {

		private final OffHeapArray array;

		OffHeapReference(final Object parent, final OffHeapArray edges) {
			super(parent, REF_QUEUE);
			this.array = edges;
		}

		void dispose() {
			// free off-heap blocks
			this.array.free();
		}
	}

	static final class OffHeapDisposer implements Runnable {
		@Override
		public void run() {
			final Thread currentThread = Thread.currentThread();
			OffHeapReference ref;

			// check interrupted:
			for (; !currentThread.isInterrupted();) {
				try {
					ref = (OffHeapReference) REF_QUEUE.remove();
					ref.dispose();

					REF_LIST.remove(ref);

				} catch (InterruptedException ie) {
					MarlinUtils.logException("OffHeapDisposer interrupted:", ie);
				}
			}
		}
	}
}
